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Extensible modular DAQ system records to SD memory cards

Posted: 07 Jun 2005 ?? ?Print Version ?Bookmark and Share

Keywords:dataq instruments? instrument? module? sd memory card? secure digital memory card?

If you're working with industrial instrumentation, data acquisition equipment supplier Dataq Instruments has some nifty new modular data-acquisition instruments that will interest you. Depending on model, Dataq's latest 14-bit eight-channel instruments either stream data to your PC, or collect data as standalone data loggers

These new modules can include isolation amplifiers as an option, and some record to SD (Secure Digital) memory cards. For their part, the DI-718B Series's SD memory cards are the same as those used in typical consumer products such as MP3 music players and digital cameras.

SD cards, available in capacities of 8MB to 1GB, are available from Dataq. They're priced from about $35 to $80; an SD card reader is available for $25.

PC-Tethered or standalone

Dataq's eight-channel instruments are available with choice of either USB (Universal serial Bus) or Ethernet interfaces. Regardless of interface, they're all powered from any 9Vdc to 36Vdc source, and come with a universal power supply for that purpose.

Isolated amplification

The optional isolated amplifier modules mate with the DI-718B instruments on an as-needed basis. Kudos to Dataq Instruments for making them modular, as that means you need purchase only what you require, which goes a long way to making these extensible systems cost-effective.

What's more, the DI-8B isolated amplifier modules are priced at roughly half of what competing products go for. The cost-per-channel is also low, coming in at about $163 for eight isolated inputs.

They're also billed by the company as the world's smallest isolated analog signal conditioners. When the modules are inserted into a DI-718B instrument, the resulting system measures about 14-by-11-by-4cm in size. Dataq says competing systems typically use two boxes, one for signal conditioning and the second for data acquisition, and that results in higher costs.


The DI-8B amplifier modules can also be mixed-and-matched within a DI-718B. This capability supports AC/DC voltage measurement from 110-mV to 160-V. You can also use them in 4mA to 20mA current loops. Other modules support thermocouple conditioning, string potentiometers, strain gauge-based transducers, and frequency and RPM (revolutions/min) conversion.

The intrinsic isolation of the DI-8B amplifiers also supports successful measurement in the presence of common-mode voltages. In fact, Dataq claims that without the degree of isolation provided by its modules, you might literally destroy similarly-priced, but non-isolated, competitive products.

Input-to output isolation is maintained up to 1kV DC or 1kV peak AC. Channel-to-channel isolation is 500V DC or peak AC.

High-end features

These systems offer additional features, many of which are usually found only on more expensive instruments as well. For example, the architecture implements a channel scan list, and its 14-bit A/D (analog-to-digital) converters run at a high sample-rate. Gain ranges have selectable factors per channel of unity, 2, 4, and 8, or 1, 10, 100, and 1000.

Built-in programmable channel scan listing permits channel numbers to be dynamically selected during scanning. That lets you precisely match signal requirements on a channel-by-channel basis.

Also, these instruments, when PC tethered, stream data to your PC at a 4800-sample/s throughput rate. Standalone configurations store data to the SD cards at a maximum sample throughput rate of 14,400 samples/s.

Data on request

Dataq's latest systems can also run as miniature data-acq servers. Operating in standalone mode, a DI-718B instrument can supply data upon request via an Ethernet network, for example.

Running it that way eliminates the need to remove an SD card and physically carry its data to a PC for subsequent analysis. Instead, you can pipe data over a LAN (local area network) to a remote PC, perhaps located on the other side of your facility, or even on the other side of the world (using the Internet cloud as your wide area network).

Support software

As you'd expect, DI-718B Series instruments are supported by ample software. WinDaq/Lite bits provide a ready-to-run no-programming environment for acquiring, displaying, recording, reviewing, analyzing, and exporting waveform information. WinDaq/Lite can be used with either the PC-tethered or standalone configurations of the modules.

WinDaq/HS is similar to WinDaq/Lite, except it supports throughput-to-disk rates of 4.8kHz. Both of these packages are supplied with the DI-718B series.

In addition, a standalone utility is included that lets a DAQ configuration be designed, and then downloaded to a DI-718B, from any local or remote PC. This utility gives you the ability to upload data stored to the SD memory as well, over the instrument's optional Ethernet interface. Finally, an ActiveX control library permits access to DI-718B functions using Windows programming languages such as VisualBASIC or C++.

Price and availability

There are four versions in the DI-718B Series. The DI-718B-U Data Acquisition Instrument, with its USB interface, is priced at $595. The DI-718B-US Data Logging Instrument, also with USB, adds $100 to the price of the DAQ version.

The DI-718B-E Data Acquisition Instrument, with its Ethernet interface, is priced at $795, and the DI-718B-ES Data Logging Instrument, also with an Ethernet interface, adds $100 more to the price of a DI-718B-E. Dataq says all models in its DI-718B Series will be available from stock beginning in July.

- Alex Mendelsohn


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